Differential pressure gauge



July 24, 1951 W. J. HUGHES DIFFERENTIAL PRESSURE GAUGE Filed Sept. 27. 1947 3 Sheets-Sheet l INVENTOR.

July 24, 1951 w. J. HUGHES DIFFERENTIAL PRESSURE GAUGE 3 Sheets-Sheet 2 Filed Sept. 27, 1947 l l I l I zug July 24, 1951 w. J. HUGHES DIFFERENTIAL PRESSURE GAUGE 3 Sheets-Sheet 3 Filed Sept. 27. 1947 RATE OF FLUW RATE 0F WHS H l /zrr//l fr 2 INVENTOR. Wade/'J ay Patented July 24, 19st 2,561,700 DIFFERENTIAL PRESSURE GAUGE Walter J. Hughes,

Chicago. lil.,

Incorporated, Chicago,

Delaware assigner to Iniilco lll.. a corporation ot Application September 27, 1947, Serial N0. 776,571 3 Claims. (C1. 73-387) This invention relates to a gauge adaptable to measure a condition represented by a pressure diiierential. such as a rate of flow gauge, or the like.

One of the objects of this invention is to provide an improved rate of flow gauge.

Another object of this invention is to provide a gauge adapted to operate from a loss in pressure between two points in a system. such as a rate of iiow gauge in a iiow conduit, or a loss of head gauge adapted to indicate the condition of a filter. or the like.

Another object of this invention is to provide a iiow gauge adapted to measure flows of dierent values and diiierent directions. such as a gauge to indicate the rate of flow through a filter system under normal operating conditions and the rate of flow o! wash water in a reversed direction and at much greater rate of iiow.

These and other objects yof my invention will be apparent from the description and claim which follow.

One most important use of my invention is a rate of ow gauge which can be a single function to indicate a rate of flow in a single direction. or a double function gauge to indicate the value and direction of flows when flows through the conduit may be in different directions and at diiierent values. However. it will be obvious that these are not the sole uses of my gauge. as it obviously is adapted to measure any condition which is. or can be, represented by a diilerential pressure, or a loss in pressure between two points of a system. For example, the single function gauge may have one side connected to the inlet of a filter and the other side connected to the outlet thereof and the gauge used to indicate the state of the filter bed. which is indicated by the amount of loss of head due to resistance to flow through the lter bed. Where a iiow is controlled to a fixed value, as it ordinarily is through a lter. the measure in loss oi head is an indication the condition of the lter bed and enables the operator to judge the time at which the ltering function should be terminated and backwashing or reconditioning should begin. Other uses of the gauge will be obvious to those skilled in the art. However. for purposes of illustration. I will describe my invention in connection with a rate of flow gauge adapted to indicate the value of a iiow through a conduit.

Brieily, my invention comprises a pair of diaphragm chambers with associated diaphragme, one chamber being connected to a point of high pressure in the system and the other to a point of low pressure. nected by a spacer bar and act in opposing directions. Movement of the spacer bar positions a lever which in turn positions a pointer which indicates the rate of ow. Motion of the lever is opposed by a tension spring, which. as is well known, exerts a force directly proportional to its elongation. Thus the pressure differential will be balanced by the force of the spring, and the pointer will be positioned along a scale, according to the magnitude of the forces.

My invention will be more readily understood from a'consideration of the more detailed description which follows and the drawings in which:

Figure 1 represents a vertical cross-sectional view of a. single function gauge, with cover and scale removed, such as that adapted to indicate the value of a flow through a system in one direction:

Figure 2 represents a back view of the gauge of Figure l, together with the ilow system in which it may be interposed;

Figure 3 is a double function time Figure 4 is a cross-sectional view of the gauge shown in Figure 3. including cover and scale dial, taken along the planes indicated by the line 4 4 in Figure 3;

Figure 5 is a front view. on a reduced scale. of the gauge shown in Figures 3 and 4.

For purposes of illustration. my invention will be described in connection with the measurement oi a iiow through a conduit such as pipe In shown in Figure 2. Various means are known for developing a diiierential pressure, or loss of pressure, between two points in a flow system. such as the use of the well known Venturi tube. .A Venturi tube is an eiiicient means of creating such a diierential and would ordinarily be preterred for use in connection with a uni-directional iiow. However such tubes are not adaptable to creating pressure differentials when flow is in a reverse direction unless associated with a complex system of piping, which it is desirable. to avoid. I, therefore. prefer to use a. xed orifice il which can be inserted in the pipe I0. The orice il can be of any suitable style, but for purposes of illustration I show an oriice plate l2 clamped between the flanges Il and Il, the assembly being held together by any suitable means. such as bolts l5. If iiow is from left to 'Ihe two diaphragms are conright in Figure 2 the pressure on the left hand side will be greater than on the right hand side. Conversely, if ow is from right to left then the pressure on the right hand side becomes higher than on the lett hand side o! the orice ii. The orice plate is provided with pressure ports I6 and l1, which are adapted to be connected to pressure conduits Il and I3. respectively, leading to the gauge. as shown. It is weil known that the downstream connection in such an orifice should be a distance below the oriilce corresponding to the position o! the in order to obtain a true head for a given flow. In my apparatus, however, in order to avoid the necessity of switching connections each time the now is reversed, I prefer to place the ports I6 and I1 adjacent to the orice plate ii and to calibrate the scale dial accordingly. Thus the dial is calibrated to ilow head values which, while varying according to the equation Flow squared=head x 2 gravity is modied by the fact that the downstream connection is out of position as explained above. Thus in order to save space and to avoid complex piping, the oriilce chamber is modified as described. and the scale dial is calibrated accordingly.

Referring first to the single function gauge shown in Figure l. The gauge mechanism is mounted on a suitable base plate 2li on the front of which is mounted a pair of opposed pressure chambers 2| and 22. As shown in the drawings these chambers may have integral mounting brackets 2id and 22a respectively which are aiiixed to the iront face ci the base plate 20 by any suitable means, such as machine screws 31. Associated with the left hand pressure chamber 2|, which in this gauge is the chamber which will be connected to the point oi greater, or higher, pressure. is a diaphragm 23 which is clamped to the face of the chamber by a suitable clamping ring 24. The diaphragm 23 is provided with relatively large centering plates 25 and 26. Similarly the opposed pressure chamber 22, which in this gauge will be connected to the point of low pressure, is provided with a diaphragm 21 which is clamped thereto by a suitable clamping ring 2li. The diaphragm 21 is provided with centering plates 20 and 30. The two clamping rings 24 and 28 are bolted to their respective chambers by any suitable means, such as machine screws 3|. It is preferred that the diaphragm chambers 2| and 22 be of identical size and that the centering plates 26 and 26 and 29 and 30 be of identical size.

The diaphragms 23 and 21 should be of very thin and strong material, such as nylon impregnated with rubber or neoprene so as to provide a huid-tight membrane of great ilexibility. For this purpose I have used diaphragms having a thickness of from 0.013 to 0.018 inch. I have used such diaphragms even with pressures of considerable value. such as 50 to 100 pounds per square inch. Such diaphragms are exceedingly strong and, in my preferred construction, the gap between the diaphragm chamber and the centering plates is quite small. For example, I have used diaphragm chambers with an inner diameter of 1% centering plates with a diameter of 11/4 inches, leaving a gap of V4 inch between the diaphragm chamber and the centering plates. The diaphragm then has an etl'ective diameter of 1% inches. an effective area oi' 1.76 square inches,

true vena contracte inches, associated with which are and permits a traverse motion of inch with respect to the neutral diaphragm position without distortion or upsetting oi diaphragm forces.

A conduit 32 leads to the pressure chamber 2i from the back of the base plate, and is adapted to be connected to a high pressure conduit as shown in Figure 2. Similarly conduit 33 leads from the interior of the diaphragm chamber 22 to the back of the base plate and is adapted to be attached to a low pressure conduit.

The two exterior diaphragm center plates 26 and 30 are heid in spaced relationship by a spacer bar 34 which is provided with a central peripheral slot 35. The assembly of centering plates and spacer bar is held in fixed position by any suit able means, such as bolts or machine screws 36.

A vertical lever 40 is mounted between the two diaphragm chambers 2| and 22. The lever 40 is supported by any suitable supporting bracket 4|, mounted on the base plate 20 (see Figure 4) to which it is pinned by a machine screw 42. A pin 43 is mounted in the lever 40 in such a manner as to be enclosed within the slot 35 on the spacer 24, so that motion of the diaphragms and the spacer 34 is imparted to the lever 40. As the motion oi' the diaphragms will be exceedingly small it is necessary that their motion be magnified to provide a pointer operating over a readily readable scale. For this reason the lever 40 is relatively long and the fulcruin point is at the lower end of the lever. The upper end of the lever is provided with a longitudinal slot 44, as shown. Associated with the lever 40 is an indicator arm 45, pivoted at its upper end on pin 46 while the lower end is provided with a pointer 41 which is bent forward, as shown in Figure 4, to pass in front of a suitable scale. The pointer arm 45 carries a pin 40 which is slidably engaged in the slot 4I of the lever 40.

A tension spring 50 is so mounted as to pull the lever toward the high pressure chamber 2i. In the drawing the tension spring 50 is shown as provided with a hook 5i which is inserted in a hole 49 in the lever 40 and the other end is mounted on a threaded spring mounting 52.. The tension of the spring can be adjusted by rotation oi the bolt 53, the threaded portion o! which engages the threaded portion oi' the spring mounting 52. Both tension of spring and spring length (free) can be adjusted by such means, for the spring length at zero tension is the important adjustment. The force oi the spring 5B is set so that when pressures in the two chambers 2l and 22 are equal the pointer 41 is pulled to the zero position. In this instance, the maximum graduation on the scale will be at the right and the zero t position at the left.

When the pressures conducted to the two chambers 2l and 22 diler then the diaphragm assemblies and the connecting spacer 34 are moved toward the right by virtue of the fact that the pressure in the left hand chamber 2l is greater than in the right hand chamber 22. Such movement of the diaphragm assembly moves the lever 40 toward the right, which motion is magnified by the means described to cause the pointer 41 to move to the right through an angle which is readily readable on an appropriate scale. Motion of the lever 40 towards the right is opposed by the tension in the spring 50, the force of which varies directly with the amount of its elongation. Thus the diaphragm assembly will come to rest at a -point in which the pressure diilerence between the two chambers is exactly balanced by the 75 torce of the spring 50 and this constitutes an accurate register ci' the amount of ilow being measured.

The apparatus shown in Figures 3, 4 and 5, is essentially the same as that shown in Figure i. The diaphragm chambers 2| and 22 are mounted in a casing a. As indicated above, this form is adapted to accurately measure the direction and value of flows going in opposite directions through the pipe Ill. In this instance, the pointer arm 45 is in a vertical position when at a zero position and there is no flow through the conduit Ill. 'I'his is shown particularly well in Figure 5 in which the pointer is shown at the zero position and moves to the right to measure a rate of ilow in one direction and moves to the left from the zero position to measure a rate of flow in the opposite direction. As shown by the markings on the scale 60, these flows do not need to be o! the same magnitude. To secure such operation it is necessary to use two springs 56a and 50h. one end of each being hooked in the slot 48a oi the lever arm 4U and the other ends held on a threaded spring mounting 52a and 52h, respectively, which are carried by bolts 53a or 53h rotatably held in brackets 55. In this instance, the hole in which the hook portion of the two springs are inserted should be a slot so that the spring which is not in use at any particular moment will be free to slide in the slot. For example, assuming that a rate of flow is being measured which causes the pointer to move to the right, then the spring 50a will be under tension but'spring 50h should be free to slide in the slot so as to avoid affecting movement of the lever arm lil.

In this form of apparatus, when the left hand chamber 2| is the high pressure chamber, the pointer Il will be moved to the right from the neutral position through an angle proportional to the pressure diiierence between the two chambers. However when the direction of flow is reversed the right hand chamber 22 becomes the high pressure chamber and the diaphragm assembly will be moved to the left and the pointer 4l will be moved to the left from the zero position through an angle corresponding to the rate of iiow. If the gauge is to be used for indicating the direction and magnitude of flows through a filter the magnitude to the flows to be measured will be quite different. In some instances, the rates or magnitude of ilow in the two directions will be equal but ordinarily this is not true of flows through filters. In lter practice it is desired to backwash. in most installations, at a rate approximating three or four times that of the iterlng flow. In such cases it is possible to equal the pointer travel in the two directions over the scale dial SII by using springs having spring rates for the same deflection in the rates of 9 to 1. That is, assuming a filtering ow at three gallons per squart foot of filter area and an alongation of the spring 50a of one. When washing at the customary washing flow of nine gallons per square foot per minute then the elongation of the spring 50h should also be one. As the pressure diii'erential varies as the square of the now, itis obvious that the spring force of spring 50h should be nine times that of Sua in order to convert the squares of the flow into angular motion of similar magnitude.

The dial scale Bil can be mounted in front oi' the mechanism but behind the forwardly bent pointer 41 as shown in Figure 4. In this embodiment the scale is shown as mounted by any suitable means. such as machine screws 6|; upon the brackets 55. The entire mechanism is enclosed 6 Y in a suitable casing, or cover 52 oi any suitable material. The casing 52 is provided with a window l2 oi glass, or other transparent material, located immediately in front of the scaleI III. When used in connection with a filter it ordinarily will be preferred that the values on the wash flow side of the gauge will be three to four times those on the rate of iiow side. as shown by the graduations on the scale 60 in Figure 5.

While I have herein described, and in the drawlng shown. illustrative embodiments of my invention it is to be understood that the invention is not limited thereto. but may comprehend other constructions, arrangement of parts, details and features. the equivalent thereof without departing from the spirit of this invention. Manifestly. the arrangement shown in capable of considerable modification by persons skilled in the art and any such modifications as are in keeping with the foregoing description and claims which follow are considered to be within the present invention.

I claim:

1. A gauge adapted to indicate the direction and magnitude of flow through a conduit comprising a casing, a pair of opposed diaphragm chambers mounted in said casing, said diaphragm chambers being adapted to be connected to points of different pressure in said conduit, diaphragms in said chambers, a spacer bar connecting said diaphragms, a lever arm pivotally pinned to a lower portion of said casing and slidably pinned to said spacer bar, a pair of tension springs, a slidable connection between each of said springs and said lever arm, one on each side thereof. whereby one of said springs is inactive while the other is under tension, and a pointer pivotally mounted at an upper portion of said casing above the upper end of said lever arm and slidably pinned to said lever arm.

2. A gauge adapted to indicate the direction and magnitude of iiows of different ranges through a conduit having a pressure differential creating restriction therein, said gauge comprising a pair of opposed diaphragm chambers, diaphragms across opposing faces of said chambers, a spacer bar connecting said diaphragms, a lever arm pivoted at it lower end and positioned by movement of said spacer bar, said lever arm having a slotted portion, tension springs slidably connected to said slotted portion, one on each side thereof, said tension springs having dilierent spring rates, the proportion of the spring rate of the larger spring to that of the smaller spring being equal to the proportion of the square of the greater iiow range to that of the lesser liow range, a pointer pivoted at its upper end and positioned by said lever arm. and means for connecting said diaphragm chambers to said conduit on opposite sides of said pressure differential creating restriction.

3. A gauge adapted to and magnitude of ows of differing ranges through a conduit having a pressure diilerentlal creating restriction therein, said gauge comprising a casing, a pair of opposed diaphragm chambers mounted in said casing, means adapted to connect said chambers 'to said conduit on opposite sides of said restriction, diaphragms across opposing faces of said chambers, a, spacer bar connecting said diaphragms, a lever arm positioned by movement of said spacer bar. said lever arm having a slotted portion, a tension spring of one spring rate slidably connected to said slotted portion on one side of said lever arm and opposindicate the direction 7 ing motion thereof in one direction. a second tan- BEFEBENCEB GITED sion spring of another spring rate slidably 00D- The following references are oi' reoord in the neoted to said slotted portion on the other side me of this ment: of said lever arm and opposing motion thereof in the other direction. the proportion of the 6 UNITED STATES PATENTE spring rate of the larger spring to that o! the Number Name Date smaller spring being equal to the proportion of 750,752 Cole Jan. 26, 1904 the square of the greater flow range to that of 2,005,773 De Florez June 25. 1935 the lesser flow range, a pointer having its fuicrum 2.052.720v MacLean et al Sept 1. 1936 above the upper end of said lever arm and slidl0 2.199.013 Sprague Apr. 30, 1940 ably pinned to the upper end of said lever'arm. 2.444.358 Maricson et al June 29. 1948 and a graduated dial mounted on said casing in a plane behind the plane of movement of said FOREIGN PATENTS pointer. r Number Country Date WALT@ J. Hugm 15 14,903 Great Britain June 27, 1910 

